Preliminary heads up ahead of 8.1’s release : The folder structure will be changing once 8.1 goes live. Once 8.1 is live and your client is updated , You will have one Data folder shared over your retail , PTR and beta installs.

All the existing folders (eg Screenshots , WTF , Errors , Logs , Cache etc etc) will be moved into retail . All executable programs like Wow,exe or BlizzardError.exe and the DLLs will also be moved into retail

Addons should work fine after the migration as the client will now be looking in the new path and the Interface folder should be moved over fine

If you have the PTR installed all it’s stuff will be under a _ptr_ (folder) . I would expect beta to be under _beta_ (folder)

Minion is all set for this change, so if you use it to install and update your addons, you won't have to worry about it. If you manually install/update, you will need to keep this change in mind.